(a) Field of the Invention
The present invention relates to apparatus and method of processing signals.
(b) Description of Related Art
Generally, a liquid crystal display (LCD) includes a pair of panels including a plurality of pixel electrodes and a common electrode and a liquid crystal (LC) layer interposed between the panels and having dielectric anisotropy. The pixel electrodes are arranged in a matrix and connected to switching elements such as thin film transistors (TFTs). The pixel electrodes are supplied with data voltages through the TFTs row by row. The common electrode ranges over an entire surface of a panel and is supplied with a common electrode. The pixel electrode and the common electrode along with the LC layer disposed therebetween form LC capacitors in circuital view, and a LC capacitor as well as a switching element is a basic element forming a pixel.
The LCD generates electric field in the LC layer by applying voltages to the electrodes, and obtains desired images by controlling the strength of the electric field to varying the transmittance of light incident on the LC layer. At this time, the polarity of the data voltages with reference to the common voltage is periodically reversed in a unit of frame, row, or dot for preventing the deterioration of liquid crystal due to long-time application of unidirectional electric field, etc.
The LCD is increasingly used for displaying motion images and the slow response time of the liquid crystal is focused on. In particular, the increase of the size and the resolution of the display devices severely require the improvement of the response time.
In detail, the slow response time of the liquid crystal makes it take a time for a pixel to reach a desired luminance. The time for obtaining the desired luminance depends on the difference between a target voltage for giving the desired luminance and a previously charged voltage across the LC capacitor of the pixel. The pixel may not reach the desired luminance for a given time if the voltage difference is large.
In order to solve the problem, dynamic capacitance compensation (DCC) for improving the response time without changing the characteristics of the liquid crystal itself is suggested. The DCC applies a voltage higher than the target voltage to the LC capacitor to reduce the time for reaching the desired luminance.
The DCC generates modified image data after comparing image data between successive two or three frames and thus it requires at least one frame memory for storing image data of a frame.
However, the frame memory increases the production cost and the area of a control board.